Synthesis of methyl 5-azido-5-deoxy-2,3- O-isopropylidenecarba- α-D- allo-hexafuranuronate, the sugar part of carbapolyoxins and carbanikkomycins

Abstract

The sugar part of carbapolyoxins and carbanikkomycins, methyl 5-azido-5-deoxy-2,3- O-isopropylidenecarba- α-D- allo-hexafuranuronate ( 16), was synthesised starting from enantiomerically enriched norborn-5-en-2-yl acetate ( 2). For the introduction of the hydroxy groups and the azido functionality the rigidity of the norbornene skeleton provided the regioselective attack of the reagents. For the key step in this synthesis, the Baeyer-Villiger oxidation of ketone 6, a method was developed, which might either be used for the synthesis of Ohno's lactone 10 or the isomeric lactone 9.